Paenibacillus sp. VT-400

Paenibacillus sp. VT-400 in Patients with Hematological Malignancies

Paenibacillus sp. VT-400 is a novel spore-forming species that was isolated from the oral cavity of patients with acute leukemia. The organism colonizes the oral cavity and is an important pathogen of pneumonia and potentially other opportunistic infections, particularly in immunocompromised hosts. Indeed, we demonstrated that Paenibacillus sp. VT-400 is capable of inducing pneumonia associated with disseminated infections that result in significant levels of mortality. Notably, prophylactic treatments, such as oral rinses, are ineffective in eradicating the spores of strain VT-400, and are therefore insufficient to reduce the bacterial load within the oropharynx and prevent aspiration pneumonia.
Our data suggest that the organism presents genetic features of pathogenic bacteria, and can trigger life-threatening infections in at-risk patients, particularly those with underlying pathologies such as hematological malignancies.

Virulence Factors

Antibiotic Resistance

Spread of Antibiotic Resistance

CITATION

Tetz G, Tetz V (2016). Genomic characterization and assessment of the virulence and antibiotic resistance of the novel species Paenibacillus sp. strain VT-400, a potentially pathogenic bacterium in the oral cavity of patients with hematological malignancies. Gut pathogens, 8(1), 1.

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Genomic characterization and assessment of the virulence and antibiotic resistance of the novel species Paenibacillus sp. strain VT-400, a potentially pathogenic bacterium in the oral cavity of patients with hematological malignancies

Paenibacillus sp. strain VT-400 was isolated from the saliva of four children with acute lymphoblastic leukemia. The genome was annotated using RAST and the NCBI Prokaryotic Genome Annotation Pipeline to characterize features of antibiotic resistance and virulence factors. Susceptibility to antibiotics was determined by the Kirby–Bauer disc diffusion method. We used a mouse model of pneumonia to study virulence in vivo. Mice were challenged with 7.5 log10–9.5 log10 CFU, and survival was monitored over 7 days. Bacterial load was measured in the lungs and spleen of surviving mice 48 h post-infection to reveal bacterial invasion and dissemination.

Results

Whole-genome sequencing revealed a large number of virulence factors such as hemolysin D and CD4+ T cell-stimulating antigen. Furthermore, the strain harbors numerous antibiotic resistance genes, including small multidrug resistance proteins, which have never been previously found in the Paenibacillus genus. We then compared the presence of antibiotic resistance genes against results from antibiotic susceptibility testing. Paenibacillus sp. strain VT-400 was found to be resistant to macrolides such as erythromycin and azithromycin, as well as to chloramphenicol and trimethoprim–sulphamethoxazole. Finally, the isolate caused mortality in mice infected with ≥8.5 log10 CFU.

Conclusions

Based on our results and on the available literature, there is yet no strong evidence that shows Paenibacillus species as an opportunistic pathogen in immunocompromised patients. However, the presence of spore-forming bacteria with virulence and antibiotic resistance genes in such patients warrants special attention because infections caused by spore-forming bacteria are poorly treatable.